Electrochemical anodization of Ti-Ni alloys with different Ni composition was carried out in an ethylene glycol base electrolyte under the various conditions to investigate the effect of crystal structure and chemical composition of the Ti-Ni alloy. X-ray diffraction patterns indicated that Ti-48.0 Ni and Ti-49.0Ni alloys were the martensitic phase at room temperature, while Ti 50.6Ni and 51.0Ni were the austenitic phase. Self-organized nanotubular oxide layers were formed on four Ti-Ni alloys. The thickness of oxide layers increased with increasing anodization time and applied voltages. Energy-dispersive X-ray analysis indicated that the nanotubular oxide layers consist of two kinds of oxides, one of which is Titanium oxide and the other is Nickel oxide. These results indicate that the growth of nanotubular oxide layer formed Ti-Ni alloys are not affected by crystal structure, but by applied voltage and anodization time.